1) Field of the Invention
The invention relates to a device for heating liquids and particularly to liquid containers having at least one heating element.
2) Description of the Prior Art
Devices for heating liquids, such as for instance kitchen equipment, laboratory equipment, rice cookers, water kettles and electric water kettles, generally comprise, in addition heating elements for heating the liquid, temperature-sensitive electrical circuits for the purpose of controlling the heating process and/or safeguarding the device against for instance overheating. A temperature-sensitive electrical circuit can for instance switch off a heating element when the heated liquid reaches a determined desired temperature. Another application is the use of a temperature-sensitive electrical circuit to prevent overheating of a heating element in the case an appliance is for instance switched on without liquid being present to which the heating element can transfer the heat.
The British patent GB 2 153 190 describes a method for manufacturing a device for heating water. The heating element described here is a substrate provided with an electrically insulating material on which a heater track is screen printed. The device is provided with a first temperature sensor for sensing steam and a second sensor for sensing a “boil dry” condition. In an embodiment variant the second sensor can be arranged adjacently of the heater track on the heating element. Thermistors are proposed as sensors.
A frequently applied alternative, for instance in water kettles, to a sensor in the form of a thermistor is formed by a bimetal switch which is thermally connected to a heating element, and can thus be used as safeguard against overheating. Such a bimetal switch for instance switches off the power supply to the heating element when the temperature of the heating element exceeds a determined value and/or switches the heating off when the heated liquid boils.